1. Field of the Invention
The present invention relates to a method for manufacturing a golf club head and, more particularly, to a method for manufacturing an integrally formed high-strength blade-type golf iron head with a thin blade.
2. Description of the Related Art
Golf club heads includes woods, irons, and putters. Early woods and irons are generally made of stainless steel or carbon steel to increase the performance of the golf club heads. New steel-type cast materials have been continuously developed in recent years and have been used to manufacture golf club heads. For example, steel type alloys containing cobalt, molybdenum, or titanium generally have a high strength (the tensile strength is higher than 250 ksi) suitable for manufacturing golf iron heads.
Golf iron heads include a cavity-back type and a blade type. A golf iron head of the cavity-back type is a design of a low center of gravity, because there are more centers of gravity distributed around the club face. Furthermore, the average distribution of the surrounding centers of gravity provides a larger sweet area, such that the tolerance of miss-hitting of a golf iron head of the cavity-back type is larger. Namely, even if the user fails to hit the center of the sweet area, the golf ball still can easily be pushed towards the target location, and the driving range is also better. Namely, the driving range is not significantly reduced by the deviation of hitting. By contrast, a blade-type golf iron head has a small, thin club face, such that the sense of feel of hitting transmitted to the hands via the club shaft will be more obvious. Whether the hit is in the sweet area or missed, it can clearly be transmitted to the hands of the user, such that the user can identify whether each hitting achieves the expected effect, providing assistance in adjustment and skill training for the user.
Thus, if the center of gravity of a blade-type golf iron head can be lowered, the blade-type golf iron head can possess the advantages of an increased sweet area and the sense of feel of hitting. With reference to FIG. 1, a blade-type golf iron head 9 includes a blade 91 having a thickness T. The center of gravity of the blade-type golf iron head 9 can be lowered if the thickness T of the blade 91 is reduced.
However, current blade-type golf iron heads are formed by forging or casting. Although casting has a cost lower than forging, current casting methods includes using a high frequency induction furnace to rapidly melt the cast materials in the atmosphere. Next, the slag and gases in the molten metal are removed by slagging and refinery steps. Static gravity pouring is then carried out. However, the cast materials for blade-type golf iron heads often include active metals (such as manganese, aluminum, silicon, cobalt, molybdenum, and titanium) that are apt to react with oxygen in the air. Thus, rigorous oxidation easily occurs during the procedures of smelting of the cast materials, increasing difficulties in melting and easily causing oxidative fire cracks due to reaction with air during pouring. As a result, appearance defects, such as sesame dot defects and black bean defects, are apt to be formed on the cast products of the blade-type golf iron heads. In worse situations, the reactive gas forms a large number of slag holes or blowholes in the cast products of the blade-type golf iron heads and, thus, adversely affects the tensile strength of the blade-type golf iron heads, limiting the thickness of the blades of the blade-type golf iron heads.
Namely, to assure that the blade of a blade-type golf iron head can meet the tensile strength standard so not to be damaged after the striking faceplate of the blade-type golf iron head has withstood cannon shots of predetermined strength and times without damage, the thickness of the blade of a current integrally formed blade-type golf iron head is still too thick (about 6.0 mm), which not only causes difficulties in lowering the center of gravity of the blade-type golf iron head but results in a heavier overall weight (about 260 g) of the blade-type golf iron head.
Furthermore, rigorous oxidation also reduces the flowability of the molten metal in the shell mold, leading to a reduced yield of the cast products of blade-type golf iron heads due to insufficient pouring or resulting in gaps in the cast products of the blade-type golf iron heads due to cold shut. The tensile strength of the cast products of the blade-type golf iron heads is also adversely affected.
Thus, improvement to conventional methods for manufacturing blade-type golf iron heads is desired.